A progressive damage model is presented for notched laminated composites subjected to tensile loading. The model is capable of assessing damage in laminates with arbitrary ply-orientations and of predicting the ultimate tensile strength of the notched laminates. The model consists of two parts, namely, the stress analysis and the failure analysis. Stresses and strains in laminates were analyzed on the basis of classical lamination theory with the consideration of material nonlinearity. Damage accumulation in laminates was evaluated by proposed failure criteria combined with a proposed property degradation model. A nonlinear finite element program, based on the model, was developed for lami nates containing a circular hole. Numerical results were compared with the experimental data on laminates containing an open circular hole. An excellent agreement was found be tween the analytical prediction and the experimental data.

An investigation was conducted to study tensile failure of laminated composites containing an open hole. This investigation was especially concerned with determining the response, type and extent of damage in composites as a function of applied load. Both an analysis and experiments were performed for graphite/epoxy composites during the study. A progressive damage analysis was developed to study the problem. The analysis was verified by an extensive comparison between the numerical calculations based on the analysis and the experimental data obtained during the investigation as well as from published literature. Different graphite/epoxy composite materials were considered in the study. Overall, good agreements were found between the calculations and the data. Based on the study, it was found that the types and extent of internal damage in the notched composites strongly depend on the ply orientation of the laminates. The types and the size of damage directly affect the strength and failure mode of the composites.

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A progressive damage model was developed for bolted joints in laminated composites which may fail in either tension mode or shear-out mode. The model is capable of assess ing damage accumulated in laminates with arbitrary ply orientations during mechanical loading and of predicting the ultimate strength of the joints which failed in tension or shear-out mode. The model consists of two parts, namely, the stress analysis and the failure analysis. Stresses and strains in laminates were analyzed on the basis of the theory of finite elasticity with the consideration of material and geometric nonlinearities. Damage accumulation in laminates was evaluated by the proposed failure criteria combined with a proposed property degradation model. Based on the model, a nonlinear finite element code was developed. Numerical results were compared with available experimental data. An excellent agreement was found between the analytical predictions and the experimental data.